The subject matter of the invention is a fuel delivery and ventilation system for use in a fuel tank of a motor vehicle.
It is known to deliver fuel from a fuel tank to the internal combustion engine of a motor vehicle by means of a pump. In order, even when the filling level in the tank is low, to ensure reliable delivery in all situations where the fuel can move away from the pump, for example when cornering or when the motor vehicle is parked on a slope, the fuel pump is often arranged in a surge chamber. In this case, the fuel is delivered into the surge chamber and the fuel pump sucks up the fuel from the surge chamber.
Moreover, further units and subassemblies are arranged in today""s fuel tanks and these likewise ensure reliable supplying of fuel under all operating conditions. These include, in particular, lines, valves, filters, pressure regulators and the ventilation system. The ventilation of a fuel tank has to be ensured both for the refueling procedure and during operation of the vehicle. For this, use is generally made of a ventilation system with which the ventilation during operation and refueling is ensured. Ventilation systems of this type often have a plurality of lines which lead from a plurality of locations in the tank to one or more compensating containers. These compensating containers are used as a liquid trap for the fuel and are arranged both within and outside the fuel tank.
A disadvantage of all these fuel delivery systems is the high outlay for the individual components with regard to their arrangement, fastening and installation. Since today""s fuel tanks have a multiplicity of internal components, a large number of installation steps are required in order to fit all of these internal components in the tank. As a consequence, the manufacturing of the tank, or of the half shells from which the fuel tank is ultimately produced by joining them together, proves to be relatively complicated, since all of the internal components have to be fastened to the tank wall and connecting elements for the fastening of the internal components have therefore to be molded onto the tank wall. This requires complicated, and therefore expensive, tools for producing the individual half shells.
The invention is therefore based on the object of providing a fuel tank in which the production and the installation can be brought about more simply and with lower costs.
The arrangement according to the invention comprises a delivery unit, which has a fuel pump arranged in a surge chamber, and a ventilation system for ventilation during operation and/or refueling with a compensating container which is arranged in the fuel tank and into which the ventilation lines open. The surge chamber and the compensating container are connected to each other and form a unit. As a result, the delivery unit and the compensating container and the ventilation system can be assembled and tested in advance and then arranged as a single unit in the fuel tank.
A wide variety of refinements are conceivable for the arrangement of the compensating container and surge chamber. In a first refinement, the compensating container can be arranged above the surge chamber. This refinement is particularly advantageous particularly in the case of tall tanks, since the compensating container can more usefully be arranged together with its ventilation lines in the upper region of the fuel tank, while the surge chamber can be fitted in the direct vicinity of the tank floor. In the case of flatter fuel tanks the surge chamber can be arranged next to the compensating container. In this case, the surge chamber and compensating container are separated from each other by a common wall.
In one advantageous refinement, the compensating container and the surge chamber are separate components which are connected to each other. The two components can subsequently be joined in a positive-locking manner as a latching, plug-in or screw connection, in a materially connected manner by bonding or welding, or with a frictional connection by means of clamping elements. In this connection, there is the option of first of all fitting all of the components, for example the fuel pump, filter, pressure regulator, suction jet pumps, filling-level sensor, in the surge chamber and then of connecting the surge chamber to the compensating container. The ventilation system can also be fitted to the compensating container in advance. The device according to the invention can be used both in injection-molded tanks and in blow-molded tanks. To this end, in an injection-molded tank the device is fitted in one of the half shells before the tank half shells are joined together. When used in a blow-molded tank, the finished device is placed in the shaped part directly prior to the blow molding.
It is also conceivable to produce the compensating container and the surge chamber integrally. The advantage here is that the two components then no longer have to be connected to each other. The component forming the compensating container and the surge chamber can be produced by means of injection molding, for example. In one refinement of this component, in which the compensating container is arranged above the surge chamber, it is advantageous to design at least the region of the surge chamber to be open, in order to make possible subsequent installation of the fuel pump and the associated components. The surge chamber can be designed to be closeable by a lid, which is designed as the base, once installation has taken place. In a similar manner to this, the compensating container can also be designed to be closeable by a lid.
A refinement has proven advantageous in which the side walls of the surge chamber are flexible in such a manner that the surge chamber is variable in its height. This ensures that the fuel delivery and ventilation system according to the invention can be adapted to the height of the fuel tank, since the height thereof varies as a consequence of the filling level. It is thereby ensured that the surge chamber is in contact with the floor of the fuel tank and the fuel is therefore sucked up at all times from the deepest point in the fuel tank. At the same time, the ventilation lines are always located in the upper region of the fuel tank, thereby ensuring reliable ventilation. The fuel delivery and ventilation system can be fixed to the upper or lower boundary wall of the fuel tank.
It further has to be ensured that the liquid fuel collecting in the compensating container is removed so as to avoid flooding of the compensating container. For this purpose, the compensating container can be equipped with a valve, in particular with a nonreturn valve. This solution is advantageous when the fuel to be removed is conducted into the surge chamber and the latter is of closed design. The nonreturn valve only opens if the hydrostatic pressure in the surge chamber is lower than the pressure in the compensating container. Flooding of the compensating container is therefore prevented at the same time. The arrangement of an active suction means using a pump has proven favorable. This may be a suction pump operated by the flow or by the cutoff quantity of a pressure regulator, or an auxiliary pump or else the fuel pump or a further stage in the fuel pump. The fuel which is removed is conducted into the fuel tank. In this connection, long lines can be dispensed with.